Control system for gas-turbine engine

ABSTRACT

In the gas-turbine engine control system having a first control inputting the outputs of sensors and controlling supply of fuel to the engine based on at least one of the inputted outputs, the first control channel includes a comparator inputting the outputs generated by the sensors and comparing change rates of the outputs with corresponding threshold values once every predetermined time period, and a transient/steady-state discriminator discriminating that the engine is in a transient state when the number of the outputs found to be equal to or greater than the corresponding threshold values are equal to or greater than a predetermined value, while discriminating that the engine is in a steady state when the number of times that the outputs are found to be smaller than the threshold values is more than half of number of comparison time. With this, it becomes possible to discriminate whether the engine is in a steady state or in a transient state including acceleration, without being affected by noise or the like.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a control system for a gas-turbine engine,more specifically a control system for a gas-turbine aeroengine used inaircraft.

2. Description of the Related Art

In gas-turbine engine control, it is necessary to discriminate whetherthe engine is in transient condition or in steady state condition and toconduct fuel supply control in response to the determination. JapaneseLaid-open Patent Application No. Hei 6(1994)-213005 teaches a techniquethat discriminates a rapid deceleration from change rate of thelow-pressure turbine speed and conducts the fuel supply control bycalculating a desired value of the high-pressure turbine speed and thelike in response thereto, so as to avoid fan stall (so-called “surge”)that is likely to occur when the engine operating condition shifts fromthe steady state to the rapid deceleration state.

However, this prior art only discriminates the shifting from the steadystate to the rapid deceleration state based on the change rate of thelow-pressure turbine speed and does not discriminate the transient stateincluding acceleration more generally.

SUMMARY OF THE INVENTION

An object of this invention is therefore to overcome the aforesaidproblem and to provide a control system for a gas-turbine engine whichcan accurately discriminate whether the engine is in transient stateincluding acceleration or in steady state.

In order to achieve the object, the present invention provides a systemfor controlling a gas-turbine engine having two turbines including atleast a low-pressure turbine and a high-pressure turbine, comprising: atleast one speed sensor generating an output indicative of a rotationalspeed of the low-pressure turbine; at least one speed sensor generatingan output indicative of a rotational speed of the high-pressure turbine;a temperature sensor generating an output indicative of a temperature ofexhaust gas exiting the low-pressure turbine; and a first controlchannel inputting the outputs of the sensors and controlling supply offuel to the engine based on at least one of the inputted outputs;wherein the first control channels includes: a comparator inputting theoutputs generated by the sensors and comparing change rates ordifference of the outputs with corresponding threshold values once everypredetermined time period; and a transient/steady-state discriminatordiscriminating that the engine is in a transient state when number ofthe outputs found to be equal to or greater than the correspondingthreshold values are equal to or greater than a predetermined value,while discriminating that the engine is in a steady state when number oftimes that the outputs are found to be smaller than the correspondingthreshold values is more than half of number of comparison time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall schematic view of a control system for agas-turbine engine according to an embodiment of this invention;

FIG. 2 is a block diagram used to explain the structures of an ECU andan FCU in the system shown in FIG. 1;

FIG. 3 is a block diagram showing the physical components constitutingthe ECU and FCU of FIG. 2;

FIG. 4 is a block diagram comprising functional blocks representingthose of the operations of the ECU of FIG. 2 involved in discriminatingtransient/steady-state operating condition and determining sensor outputacceptability;

FIG. 5 is a block diagram showing three-value comparison conducted inthe acceptability determination block of FIG. 4;

FIG. 6 is a diagram used to explain selection of a signal usable as acontrol signal based on the result of the three-value comparison of FIG.5 and concomitant acceptability determination for checking whether thesignal is abnormal;

FIG. 7 is a block diagram showing four-value comparison conducted in theacceptability determination block of FIG. 4;

FIG. 8 is a block diagram showing comparison with a remaining value whenthe three values in the four-value comparison of FIG. 7 is abnormal;

FIG. 9 is a diagram used to explain selection of a signal usable as acontrol signal based on the result of the four-value comparison of FIG.8 and concomitant acceptability determination for checking whether thesignal is abnormal; and

FIG. 10 is a block diagram showing in detail the configuration of thetransient/steady-state discrimination block of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Control system for a gas-turbine engine according to preferredembodiment of this invention will now be explained with reference to thedrawings.

FIG. 1 is an overall schematic view of a control system for agas-turbine engine according to an embodiment of this invention.

The explanation will be made taking a gas-turbine aeroengine foraircraft as an example of the gas-turbine engine. Four types ofgas-turbine aeroengines are commonly used in aircraft: the turbojetengine, turbofan engine, turboprop engine and turboshaft engine. Atwo-spool (shaft) turbofan engine will be taken as an example in thefollowing explanation.

In FIG. 1, reference numeral 10 designates a turbofan engine(gas-turbine engine; hereinafter referred to as “engine”). Referencenumeral 10 a designates its main engine unit. The engine 10 is mountedat an appropriate location of an airframe (not shown). The engine 10 isequipped with a fan 12 (rotor blades) that sucks in air while rotatingrapidly. A rotor 12 a is formed integrally with the fan 12. The rotor 12a and a stator 14 facing it together form a low-pressure compressor 16that compresses the sucked-in air and pumps it rearward.

A duct (bypass) 22 is formed in the vicinity of the fan 12 by aseparator 20. Most of the air pulled in passes through the duct 22 to bejetted rearward of the engine without being burned at a later stage (inthe core). The force of the air accelerated rearward by the fan producesa force of reaction that acts on the aircraft (not shown) as apropulsive force (thrust). Most of the propulsion is produced by the airflow from the fan.

The air compressed by the low-pressure compressor 16 flows rearward to ahigh-pressure compressor 24 where it is further compressed by a rotor 24a and a stator 24 b and then flows rearward to a combustion chamber 26.

The combustion chamber 26 is equipped with fuel nozzles 28 that aresupplied with pressurized fuel metered by an FCU (Fuel Control Unit) 30.The FCU 30 is equipped with a fuel metering valve 32. Fuel pumped by afuel pump (gear pump) 34 from a fuel tank 36 located at an appropriatepart of the airframe is metered by the fuel metering valve 32 andsupplied to the fuel nozzles 28 through a fuel supply line 38.

The sprayed fuel is mixed with compressed air exiting the high-pressurecompressor 24 and the mixture is burned after being ignited at enginestarting by an exciter (not shown in FIG. 1) and a spark plug (notshown). Once the air-fuel mixture begins to burn, the air-fuel mixturecomposed of compressed air and fuel is continuously supplied and burned.

The hot high-pressure gas produced by the combustion is sent to ahigh-pressure turbine 40 and rotates the high-pressure turbine 40 athigh speed. The high-pressure turbine 40, more specifically its rotor,is connected to the rotor 24 a of the high-pressure compressor 24 by ahigh-pressure turbine shaft 40 a. The rotor 24 a is therefore alsorotated.

After driving the high-pressure turbine 40, the hot high-pressure gas issent to a low-pressure turbine 42, which rotates at relatively lowspeed. The low-pressure turbine 42, more precisely its rotor, isconnected to the rotor 12 a of the low-pressure compressor 16 through alow-pressure turbine shaft 42 a. The rotor 12 a and the fan 12 aretherefore also rotated. The high-pressure turbine shaft 40 a and thelow-pressure turbine shaft 42 a are provided in a dual coaxialstructure.

The hot high-pressure gas passing through the low-pressure turbine 42(the turbine exhaust gas) is mixed with the air stream passing throughthe duct 22 without compression or combustion and the combined flow isjetted rearward of the engine through a jet nozzle 44.

An accessory drive gearbox (hereinafter referred to as “gearbox”) 50 isattached through a stay 50 a to the undersurface at the front end of themain engine unit 10 a. An integrated starter/generator (hereinaftercalled “starter”) 52 is attached to the front of the gearbox 50. The FCU30 is located at the rear of the gearbox 50.

The engine 10 is started by operating the starter 52 to rotate a shaft56. The rotation is transmitted to the high-pressure turbine shaft 40 athrough a drive shaft 58 (and a gear mechanism including a bevel gearetc.; not shown) so as to pull in air needed for combustion.

The rotation of the shaft 56 is also transmitted to a PMA (PermanentMagnet Alternator) 60 and the high-pressure fuel pump 34. The fuel pump34 is therefore driven to spray fuel from the fuel nozzles 28 asexplained above. The resulting air-fuel mixture is ignited to startcombustion.

When the engine 10 reaches self-sustaining operating speed, the rotationof the high-pressure turbine shaft 40 a is transmitted back through thedrive shaft 58 (and the gear mechanism including the bevel gear etc.) tothe shaft 56 to drive the fuel pump 34 and also drive the PMA 60 and thestarter 52. The PMA 60 therefore generates electricity and the starter52 supplies power to equipment in and on the airframe (not shown).

An N1 sensor (speed sensor) 62 installed near the low-pressure turbineshaft 42 a of the engine 10 outputs a signal proportional to the speedof the low-pressure turbine (speed of the low-pressure turbine shaft 42a) N1. An N2 sensor (speed sensor) 64 installed near the shaft 56outputs a signal proportional to the speed of the high-pressure turbine(speed of the high-pressure turbine shaft 40 a) N2. Thus, the N1 sensor62 and the N2 sensor 64 are installed at or near the engine 10 and eachgenerate an output indicative of the speed of the turbine.

A T1 sensor (temperature sensor) 68 and a P1 sensor (pressure sensor) 70installed near an air intake 66 at the front of the main engine unit 10a output signals proportional to the temperature T1 and the pressure P1of the inflowing air at that location. A P0 sensor (pressure sensor) 72installed inside an ECU (Electronic Control Unit) explained belowoutputs a signal proportional to atmospheric pressure P0 acting on theengine 10. A temperature sensor (not shown) provided inside the ECUoutputs a signal proportional to the temperature of the ECU.

A P3 sensor (pressure sensor) 74 installed downstream of the rotor 24 aoutputs a signal proportional to the output pressure P3 of thehigh-pressure compressor 24. An EGT sensor (temperature sensor) 76installed at an appropriate location downstream of the low-pressureturbine 42 outputs a signal proportional to the exhaust gas temperatureEGT (temperature of the exhaust gas exiting the low-pressure turbine42). Thus, the EGT sensor 76 is installed at the engine and generates anoutput indicative of a temperature of exhaust gas exiting the turbine.

The aforementioned ECU (designated by reference numeral 80) isincorporated at an upper end position of the main engine unit 10 a. Theoutputs of the sensors mentioned above are sent to the ECU 80.

The ECU 80 and the FCU 30 are illustrated in the block diagram of FIG.2, with the overall configuration of the FCU 30 being shown in detail.

In addition to the group of sensors set out above, a TLA (thrust leverangle) sensor 84 installed near a thrust lever (throttle lever) 82provided near the pilot's seat (cockpit; not shown) outputs a signalproportional to the thrust lever angle or position TLA set or inputtedby the pilot (corresponding to the pilot desired thrust). The output ofthe TLA sensor 84 is also forwarded to the ECU 80. In FIG. 2, and alsoin FIG. 3 discussed later, the sensors (P0 sensor, TLA sensor etc.) areindicated by the symbols for the parameters they detect (P0, TLA etc.).

An FMVP sensor (valve position sensor; not shown in FIG. 2) installed atan appropriate location in the FCU 30 outputs a signal proportional tothe valve position FMVP of the fuel metering valve 32. The output of theFMVP sensor is also forwarded to the ECU 80.

The ECU 80 is also connected with a CAN (Control Area Network)communications interface unit 88 through which it receives (or sends)pilot-selected commands 90 from devices other than the thrust lever 82,data from an on-board computer (Air Data Computer or ADC) 92 (e.g., Machnumber Mn, (pressure) altitude ALT and outside air temperature (totalair temperature TAT and (absolute) surface air temperature SAT)) anddata from an ECU 94 of a second engine (not shown). The data in the ECU80 are sent through the communications interface unit 88 to be displayedon a display 96 located in the cockpit.

The ECU 80 is activated once every 10 msec (millisecond) to performoperating condition (i.e., transient/steady-state) discrimination andsensor output acceptability determination based on the inputted valuesand, once every 40 msec, calculates a command value (control input ormanipulated variable) Wf for controlling the quantity of fuel to besupplied to the engine 10 (fuel flow rate), in response to the thrustlever position TLA (pilot desired thrust), so as to decrease thedifference between the low-pressure turbine shaft speed (low-pressureturbine speed) N1 and a desired speed N1com. The calculated commandvalue Wf is sent to the FCU 30 as an energizing current command valuefor a torque motor 98.

The ECU 80 monitors whether or not the detected values of thelow-pressure turbine speed N1 and a high-pressure turbine speed N2exceeds corresponding limit values (e.g., values set to 107% of therespective maximum speeds). When either of the detected low-pressureturbine speed N1 and the high-pressure turbine speed N2 exceeds thelimit value, the ECU 80 makes an overspeed discrimination and thendetermines and sends to the FCU 30 the torque motor 98 energizingcurrent command value for reducing the fuel flow rate to the engine 10to a predetermined value, specifically to zero or a minimal value.

In addition, the ECU 80 determines the command value Wf to regulate theflow rate of fuel to the engine 10 so as to decrease the differencebetween the change rate N2 dot of the detected high-pressure turbinespeed N2 (derivative of N2; acceleration/deceleration factor) and adesired acceleration/deceleration factor N2 dotcom. Specifically, theECU 80 determines an energizing current command value for the torquemotor 98 and sends it to the FCU 30.

The FCU 30 is equipped with a low-pressure fuel pump 100 that pumps fuelfrom the fuel tank 36 (not shown in FIG. 2) and supplies it to thehigh-pressure (fuel) pump 34 through a filter (and oil cooler) 102. Thehigh-pressure pump 34 raises the fuel to a high pressure and supplies itto the fuel metering valve 32. The fuel metering valve 32 is connectedwith the torque motor 98 that sets its spool position. The flow rate ofthe fuel pressurized by the fuel pump 34 is therefore adjusted (metered)by the fuel metering valve 32 according to the spool position thereof.The metered fuel is supplied to the fuel nozzles 28 through a shutoffvalve 104, a drain valve 106 and a shutoff mechanism 108. The ECU 80calculates the command value Wf indicating the flow rate of fuel to besupplied to the engine 10 at 40 msec intervals. The calculated commandvalue Wf is used to control the supply of fuel so as to achieve the fuelflow rate calculated by the FCU 30.

An emergency stop switch 110 is connected to the low-pressure turbineshaft 42 a. If the low-pressure turbine shaft 42 a should be displacedfor some reason, the emergency stop switch 110 will turn on to operatethe shutoff mechanism 108 and mechanically block supply of fuel to thefuel nozzles 28. In addition, a solenoid 112 is provided in associationwith the shutoff valve 104. The solenoid 112 is responsive to thepilot-selected command 90 for operating the shutoff valve 104 to blocksupply of fuel to the fuel nozzles 28.

FIG. 3 is a block diagram showing the physical components constitutingthe ECU 80 and FCU 30.

Because the engine 10 is a gas-turbine aeroengine, the ECU 80 and FCU 30are composed of a primary lane (first control channel or system) 200 anda secondary lane (secondary control channel or system) 202, respectivelyequipped with a CPU 200 a and CPU 202 a for conducting the aforesaidoperations, a monitor CPU 200 b and monitor CPU 202 b for monitoring theoperation of the CPU 200 a and CPU 202 a, and WDTs (watchdog timers) 200c and 202 c for monitoring the operation of the monitor CPUs. When it ismonitored to detect that an abnormal condition has arisen in the lane200, the lane 202 conducts fuel supply control in place of the lane 200.

The two CPUs 200 a and 202 a operate as the ECU 80 and FCU 30. That is,they use the outputs of the sensors (shown there) to calculate theenergizing current command value for supply to the torque motor 98 andforward the calculated value through servo drivers 200 d, 202 d (notshown in FIG. 2) to the torque motor 98. (The operation of the servodrivers 200 d, 202 d is monitored by monitors (monitor circuits) 200 e,202 e.) As is clear from FIG. 3, the torque motor 98 actually comprisestwo torque motors, one designated 981 (for the primary lane 200) and theother designated 982 (for the secondary lane 202). So long as the CPU200 a of the primary lane 200 operates normally, only the primary laneoutput is sent to the torque motor 98 (the torque motor 981).

Moreover, two or more of many of the aforesaid various sensors are alsoprovided. As shown, three TLA sensors 84 are provided, and their outputsare inputted to the two lanes 200, 202. Two each of the N1 sensor 62,the EGT sensor 76, and the FMVP sensor (not shown in FIG. 2) areprovided, and their outputs are inputted to the two lanes 200, 202.Further, four N2 sensors 64 are provided, two (designated A and B) foreach lane. The outputs of the sensors A and B of each pair are inputtedto the associated lane 200, 202.

The N2 sensors 64 are made of magnetic pickups. Four of the samestructure are installed near the shaft 56 with proximity to each other.The N1 sensors 62 are also made of magnetic pickups of the samestructure. Two are installed near the low-pressure turbine shaft 42 a.Also in case of each of the other sensors, a plurality of sensors of thesame structure are installed. Sensors of the same type are configured toproduce identical outputs.

The outputs of the P1 sensor 70 and P0 sensor 72 are inputted to thelane 200, and the outputs of the P3 sensors 74 are inputted to only thelane 202. The reason for inputting the outputs of these sensors only toone or the other of the two lanes 200, 202 is that they are lesssignificant than the outputs of the N1 sensors 62, N2 sensors 64 andother sensors that detect turbine speed.

Next, the operation of discriminating transient/steady-state operatingcondition and the operations for determining signal output acceptabilityamong of the operations performed by the ECU 80 will now be explained.

FIG. 4 is a block diagram illustrating these operations. Basically, thedrawing comprises functional blocks representing the operationsperformed by the ECU 80, specifically the operations performed inparallel by the CPUs 200 a, 202 a among the four CPUs discussed in theforegoing.

The aforesaid sensor outputs indicating the operating condition of theengine 10 (i.e., the outputted values) are first sent to a low-passfilter (not shown) for removal of noise components. Then, after beingsubjected to waveform shaping, they are sent to a counter or the likefor conversion to parameters indicating the operating condition (e.g.,conversion of the outputs of the N1 sensors 62 to rpm equivalentvalues), and forwarded to an initial checking block (determiner) 300once every 10 msec for checking or determining whether they are withinsuitably determined permissible ranges. The cutoff frequency of thelow-pass filter is set or defined in accordance with the sensor outputsso as to remove noise components of the sensor outputs as much aspossible, thus removing noise components superimposed on the sensoroutputs.

The sensor outputs include the outputs of all of the foresaid sensors,including the outputs of the N1 sensors 62 indicative of thelow-pressure turbine speed and the outputs of the N2 sensors 64indicative of the high-pressure turbine speed. At least two of each typeof sensor are provided. The outputs of the four N2 sensors 64, two foreach of the lanes 200 and 202, are processed as explained in thefollowing.

The output of the initial checking block 300 is successively sent to amalfunction discrimination block 302, where the number of times that thesuccessively-sent outputs are found to be outside the permissible rangesis counted and it is discriminated whether the sensor (correspondingthereto) is faulty.

The output of the malfunction discrimination block 302 is sent to anoutput separation block 304. The output of the initial checking block300 is also sent to the output separation block 304 unmodified. Theoutput separation block 304 operates based on the discrimination resultof the malfunction discrimination block 302 to separates or divide thoseof the inputted sensor outputs that have not been found to be faultyinto values for the respective types and then output them. Any sensoroutput that the initial checking block 300 refrained from determining,the initial checking block 300 outputs it by attaching it with atemporary-suspension flag.

In FIG. 4, “4 values OK” signifies that all four of the N2 sensors 64have been found to be normal, “3 values OK” signifies that three of thefour of the N2 sensors 64 have been found to be normal, “2 values OK”signifies that two of the four N2 sensors 64 have been found to benormal, and “1 value OK” signifies that one of the four N2 sensors 64has been found to be normal. “All NG” signifies that all outputs of theN2 sensors 64 have been found to be faulty (NG means no good).

The TLA sensors 84 and other sensors are treated similarly, so that “3values OK” signifies that all outputs of a sensor type having threeoutputs, such as the TLA sensors, have been found to be normal, “2values OK” signifies that two outputs among three outputs have beenfound to be normal and that both of the two outputs of the N1 sensors 62have been found to be normal, and “1 value OK” signifies that one outputof the two outputs of the N1 sensor 62 has been found to be normal. “AllNG” again signifies that all outputs of the sensors of the typeconcerned have been found to be faulty.

The output of the output separation block 304 is sent to an outputselection block 306. Any sensor output that the initial checking block300 refrained from determining and forwarded attached with thetemporary-suspension flag is also sent to the output selection block306. The output selection block 306, on the one hand, eliminates sensoroutputs on which determination has not been passed and, on the otherhand, selects the signals to be compared, whereafter it sends them to anacceptability determination block (three-value comparator and four-valuecomparator) 308, which compares outputs of the same type with eachother(s) to determine whether they are within a range that allows themto be considered identical, thereby discriminating whether they aresensor outputs usable for fuel supply control.

The “comparison” referred to in the acceptability determination block308 will be explained. When only one value is inputted, there is novalue to compare with each other and the value is outputted as a controlsignal without modification. Since only a single control signal isoutputted in this case, one of the lanes 200, 202 refers to the signalinput to the other lane.

When two values are to be compared, specifically, discrimination is madeas to whether they both fall in a range that allows them to beconsidered identical. When they are within such a range ofpermissibility, two signals are outputted as control signals, one toeach of the lanes 200, 202.

Similar ranges are also established for the other parameters but willnot be explained here in detail. The ranges are established usingdifferent values depending on whether the operating condition of theengine 10 is in transient or steady state. One or the other is thereforeselected based on the operating condition discrimination resultexplained later. The ranges are also used in the three-value comparisonand the four-value comparison discussed next.

In three-value comparison, two-value comparison is done three times asshown in FIG. 5. The comparison result is determined as shown in FIG. 6and used as the basis for selecting a signal usable as the controlsignal and also for determining signal abnormality. Referring to FIG. 3by way of example, “A” is the sensor output received by the laneconcerned, “B” is the sensor output received by the other lane, and “C”is the sensor output that is inputted through the CAN communicationssystem. The assigned symbols (A, B and C) indicate priority (i.e., A issuperior to B; B is superior to C). Thus, when the determination is thesame for all sensor signals, A is used as the control signal.

As shown in FIG. 6, discrimination is made in accordance with theillustrated logic based on the comparison results. Case 1 is when noabnormal signal has been found, Case 2 is when one abnormal signal hasbeen found, and Case 3 is when all signals have been found to beabnormal. In Case 3, all of the sensor outputs are discriminated to beabnormal and when one of them is in use as the control signal, it isfixed (frozen) at its value and maintained in use, and a warning isissued. In Case 1 whose “A” is followed by an encircled 2, “A” isdetermined to be probably most reliable because some probability ofmalfunction occurrence is present for “B” and “C” though very slight.

As shown in FIG. 7, four-value comparison is done by conductingtwo-value comparison three times using three of the four values and thencomparing the signals (sensor outputs) found normal with the fourthvalue. Since the sensor having four outputs is only the N2 sensor 64,“A” is the output of the N2 sensor A received by the lane concerned, “B”is the output of the N2 sensor A received by the other lane, “C” is theN2 sensor B received by the lane concerned and “D” is the output of theN2 sensor B received by the other lane. As mentioned above, the assignedsymbols (A, B, C and D) indicate priority. Therefore, three-valuecomparison is performed on “A”, “B” and “C” of higher priority in theorder mentioned and when all are found to be normal (Case 1), or whenone of the three values is found to be an abnormal signal (Case 2),two-value comparison is performed between these and “D”, whose priorityis the lowest. Aside from the point that no warning is issued, thethree-value comparison itself does not differ from that shown in FIG. 6.

As shown in FIG. 7, when the three-value comparison result is Case 1,the result of the two-value comparison with “D” is either that the fouroutputs are normal (All Signals Normal) or that “D” is abnormal (SingleFail). When the three-value comparison result is Case 2, the result ofthe two-value comparison with “D” is either that one of the four outputsis abnormal (Single Fail) or that “D” and one other output are abnormal(Double Fail).

When the three-value comparison result is Case 3, three-value comparisonwith “D” is performed and, if possible, the signal to be used isselected. The comparison logic for this is shown in FIG. 8 andacceptability determination based on the comparison result is shown inFIG. 9. Case 1 and Case 2 in FIG. 9 indicate cases in which selection ofthe signal to be used is made by re-comparison with “D”. As shown, there-comparison with “D” sometimes results in selection as the signal tobe used of one of the “A”, “B” and “C” signals that has once been foundabnormal. In Case 3 of FIG. 9, similarly to in Case 3 of FIG. 6, all ofthe sensor outputs are discriminated to be abnormal, and when one ofthem is in use as the control signal, it is fixed (frozen) at its valueand maintained in use, and the warning is issued.

The explanation of FIG. 4 will be continued. The output of the initialchecking block 300 is sent to a transient/steady-state discriminationblock (range changer) 310 which discriminates the operating condition ofthe engine 10.

FIG. 10 is a block diagram showing in detail the configuration of thetransient/steady-state discrimination block 310.

As shown in this drawing, the sensor outputs (parameters) used in thetransient/steady-state discrimination are one each of the outputs of theN1 sensors 62, the two (A and B) N2 sensors 64 and EGT sensors 76 andthe outputs of the P3 sensors 74. (Specifically, the high-priorityoutputs “A” are used insofar as they are found to be normal.)Specifically, the discrimination of the primary lane 200 is done usingthe four sensor outputs N1, N2A, N2B and EGT, while the discriminationof the secondary lane 202 is done using five sensor outputs, namely, theaforesaid four sensor outputs plus output P3. The reason for includingP3 among the parameters for discrimination in the secondary lane 202 isthat the discrimination in the secondary lane 202 needs to be conductedwith greater care because the lane 202 is a secondary lane subjected tofuel supply control in place of the primary lane 200 when a malfunctionhas occurred in the primary lane 200.

The four or five outputs are sent to a change rate threshold block(comparator) 310 a once every 10 msec (predetermined time period) to becompared with change rate threshold values predefined for the individualsensors.

As shown in FIG. 10, the change rate threshold block 310 a forwards theresults of comparing the inputted values with the correspondingthreshold values to a discrimination block 310 b. The discriminationblock 310 b uses the comparison results to discriminate the operatingcondition once every 40 msec. Basically, the discrimination is madebased on the majority rule. Specifically, in the case of the primarylane 200, the engine 10 is discriminated to be in transient state whentwo or more (half or more) of the four values are equal to or greaterthan the corresponding threshold values and is discriminated to be insteady state when two or more of the four values are found to be smallerthan the corresponding threshold values three consecutive times or threeout of four times. The comparison is made between the inputted valuesand the threshold values once every 10 msec, so that comparison is madefour times within a period of 40 msec. When the number becomes the samebetween two like values among the four values, one of the N2 sensor 64outputs is eliminated and the remaining three values are compared witheach others such that the discrimination result is in the majority isgenerated.

In the case of the secondary lane 202, the engine 10 is discriminated tobe in transient state when three or more of the five values are equal toor greater than the corresponding threshold values. On the other hand,the engine 10 is discriminated to be in steady state when three or moreof the five values are found to be smaller than the correspondingthreshold values three consecutive times or three times out of fourtimes.

In discrimination of the lanes 200 and 202 using TLA, the engine 10 isfound to be in transient state when two or more of three values areequal to or greater than the corresponding threshold values. On theother hand, the engine 10 is found to be in steady state when two ormore of three values are found to be smaller than the correspondingthreshold values three consecutive times or three out of four times.

Although discrimination is explained in the foregoing as being madeusing the change rate of values outputted once every predetermined timeperiod, it is possible to calculate the differences between like valuesoutputted once every predetermined time period and use them as thresholdvalues.

The transient/steady-state discrimination block 310 outputs thediscrimination result.

The explanation of FIG. 4 will be continued. The discrimination resultof the transient/steady-state discrimination block 310 is sent to theacceptability determination block 308. In accordance with thediscrimination result, the acceptability determination block 308 selectsand uses one or the other of the ranges for the transient and steadystates established beforehand as ranges of permissibility (within whichvalues can be considered identical). It also effects appropriate fuelsupply control based on the discrimination result of thetransient/steady-state discrimination block 310.

With respect to N1, P3, EGT and the like, a composite signal generator312 produces a composite signal using values estimated from otherparameters and the acceptability determination block 308 again makes anacceptability determination through comparison therewith.

As described above, the embodiment is configured to have a system forcontrolling a gas-turbine engine having two turbines including at leasta low-pressure turbine 42 and a high-pressure turbine 40, comprising: atleast one speed sensor (N1 sensor 62) generating an output indicative ofa rotational speed of the low-pressure turbine; at least one speedsensor (N2 sensor 64) generating an output indicative of a rotationalspeed of the high-pressure turbine; a temperature sensor (EGT sensor 76)generating an output indicative of a temperature of exhaust gas exitingthe low-pressure turbine; and a first control channel (primary lane 200)inputting the outputs of the sensors and controlling supply of fuel tothe engine based on at least one of the inputted outputs; wherein thefirst control channel includes: a comparator (change rate thresholdblock 310 a) inputting the outputs generated by the sensors andcomparing change rates or difference of the outputs with correspondingthreshold values once every predetermined time period; and atransient/steady-state discriminator (transient/steady-statediscrimination block 310) discriminating that the engine is in atransient state when the number of the outputs found to be equal to orgreater than the corresponding threshold values are equal to or greaterthan a predetermined value, more specifically the two or more of fouroutputs or three or more of five are equal to or greater than thecorresponding threshold values, while discriminating that the engine isin a steady state when the number of times that the outputs are found tobe smaller than the corresponding threshold values is more than half ofnumber of comparison time, more specifically three consecutive times orthree out of four times. With this, it becomes possible to discriminatewhether the engine 10 is in a steady state or in a transient stateincluding acceleration, without being affected by noise or the like.

Further, the system is configured to include a second control channel(secondary lane 202) controlling supply of fuel to the engine, in placeof the first control channel when an abnormality condition arises in thefirst control channel and the second control channel has thetransient/steady-state discriminator (transient/steady-statediscrimination block 310). With this, in addition to the effectmentioned above, if the discrimination results of the two controlchannels are different from each other, it becomes possible to estimatethat an abnormality has occurred in the sensor outputs and to copetherewith appropriately.

Further, one of the transient/steady-state discriminators(transient/steady-state discrimination block 310) of the first andsecond control channels, more precisely the second control channel isconfigured to have a fourth sensor (more specifically the P3 sensor 74).Accordingly, when the P3 sensor 74 that detects the output pressure ofthe compressor driven by the high-pressure turbine 74 is provided as thefourth sensor, for example, since the change in the operating conditionoccurs at the high-pressure side earlier than that at the low-pressureside, it becomes possible to discriminate the change in the operatingcondition with accuracy. Moreover, when the discrimination results inthe two control channels are different from each other, since it becomespossible to predict the possibility that surge has occurred, it becomespossible to cope therewith.

Further, each of the first and second control channels includes: anacceptability determiner (acceptability determination block 308)determining whether the outputs generated by the sensors of a same typeare within a range that allows the outputs to be considered identical todetermine the sensor output that is usable in the fuel supply control;and a range changer (acceptability determination block 308) changing therange based on the determined operating condition. With this, inaddition to the effects mentioned above, it becomes possible todetermine whether any one of the sensor outputs is usable in the fuelsupply control and to conduct the fuel supply control moreappropriately.

Further, the embodiment is configured to have a system for controlling agas-turbine engine having at least one turbine (high-pressure turbine40), comprising: a first group of two speed sensors (N2 sensors 64)installed at or near the engine and each generating an output indicativeof a rotational speed of the turbine; a second group of two speedsensors installed at or near the engine and each generating an outputindicative of the rotational speed of the turbine; a first controlchannel (primary lane 200) inputting the outputs of the first group ofspeed sensors and controlling supply of fuel to the engine based on theinputted outputs; and a second control channel (secondary lane 202)inputting the outputs of the second group of speed sensors andcontrolling supply of fuel to the engine based on the inputted outputs,in place of the first control channel when an abnormality conditionarises in the first control channel; wherein the first and secondcontrol channels include: three-value comparator (acceptabilitydetermination block 308) inputting at least four outputs (values)generated by the first and second groups of speed sensors and comparingthem with each other to determine whether at least three of the fouroutputs are within a range that allows the three to be consideredidentical; and four-value comparator (acceptability determination block308) inputting a result of comparison at the three-value comparator andcomparing the at least three with a remaining one of the four outputs todetermine whether the four outputs are within the range that allows thethree to be considered identical to the remaining one and determiningwhether each of the four outputs is the output that is usable in thefuel supply control.

More specifically, the embodiment is configured to have a system forcontrolling a gas-turbine engine having at least a low-pressure turbine42 and a high-pressure turbine 40, comprising: a low-pressure turbinespeed sensor (N1 sensor 62) generating an output indicative of arotational speed of the low-pressure turbine 42; two high-pressureturbine speed sensors (N2 sensors 64) installed at or near the engineand each generating an output indicative of a rotational speed of thehigh-pressure turbine 40; a temperature sensor (EGT sensor 76)generating an output indicative of a temperature of exhaust gas exitingthe turbine; a second group of the low-pressure turbine speed sensor,the high-pressure turbine speed sensors and the temperature sensors; afirst control channel (primary lane 200) inputting the outputs of thefirst group of speed sensors and controlling supply of fuel to theengine based on the inputted outputs; and a second control channel(secondary lane 202) inputting the outputs of the second group ofsensors and controlling supply of fuel to the engine based on theinputted outputs, in place of the first control channel when anabnormality condition arises in the first control channel; wherein thefirst and second control channels include: three-value comparator(acceptability determination block 308) inputting at least four outputsgenerated by the first and second groups of speed sensors and comparingthem with each other to determine whether at least three of the fouroutputs are within a range that allows the three to be consideredidentical; and four-value comparator (acceptability determination block308) inputting a result of comparison at the three-value comparator andcomparing the at least three with a remaining one of the four outputs todetermine whether the four outputs are within the range that allows thethree to be considered identical to the remaining one and determiningwhether each of the four outputs is the output that is usable in thefuel supply control.

With this, through the three-value comparison and four-value comparison,when the high-pressure turbine speed sensor (N2 sensor 64) or the likeis installed by plural numbers, it becomes possible to accurately selectthe sensor outputs that are usable in the fuel supply control, therebyimproving the control accuracy.

Further, it is configured such that at least one of the three-valuecomparator and the four-value comparator determines the output that isnot usable in the fuel supply control. With this, in addition to theeffects mentioned above, it becomes possible to avoid the abnormalsignal from being used in the control, thereby further improving thecontrol accuracy.

Further, it is configured such that the system further includes: atemperature sensor (EGT sensor 76) installed at the engine andgenerating an output indicative of a temperature of exhaust gas exitingthe turbine; a transient/steady-state discriminator(transient/steady-state discrimination block 310) inputting at least theoutput of the temperature sensor and at least one of the four outputsgenerated by the first and second groups of speed sensors and comparingat least one of change rates and differences of the outputs withcorresponding threshold values once every predetermined time period todetermine whether operating condition of the engine is in a transientstate or in a steady state; and a range changer (acceptabilitydetermination block 308) changing the range based on the determinedoperating condition.

Further, it is configured such that the system further includes: atransient/steady-state discriminator (transient/steady-statediscrimination block 310) inputting the outputs generated by thelow-pressure turbine speed sensor (N1 sensor 62), the high-pressureturbine speed sensor (N2 sensor 64) and the temperature sensor (EGTsensor 76) and comparing change rates and differences of the outputswith corresponding threshold values once every predetermined time periodto determine whether operating condition of the engine is in a transientstate or in a steady state; and a range changer (acceptabilitydetermination block 308) changing the range based on the determinedoperating condition.

Although a turbofan engine has been used as an example of a gas-turbineaeroengine in the foregoing embodiment, the engine can instead be aturbojet engine, turboprop engine, turboshaft engine or the like.

Japanese Patent Application Nos. 2004-106421 filed on Mar. 31, 2004, isincorporated herein in its entirety.

While the invention has thus been shown and described with reference tospecific embodiments, it should be noted that the invention is in no waylimited to the details of the described arrangements; changes andmodifications may be made without departing from the scope of theappended claims.

1. A system for controlling a gas-turbine engine having two turbinesincluding at least a low-pressure turbine and a high-pressure turbine,comprising: at least one speed sensor generating an output indicative ofa rotational speed of the low-pressure turbine; at least one speedsensor generating an output indicative of a rotational speed of thehigh-pressure turbine; a temperature sensor generating an outputindicative of a temperature of exhaust gas exiting the low-pressureturbine; and a first control channel inputting the outputs of thesensors and controlling supply of fuel to the engine based on at leastone of the inputted outputs; wherein the first control channel includes:a comparator inputting the outputs generated by the sensors andcomparing change rates or difference of the outputs with correspondingthreshold values once every predetermined time period; and atransient/steady-state discriminator discriminating that the engine isin a transient state when number of the outputs found to be equal to orgreater than the corresponding threshold values are equal to or greaterthan a predetermined value, while discriminating that the engine is in asteady state when number of times that the outputs are found to besmaller than the corresponding threshold values is more than half ofnumber of comparison time.
 2. The system according to claim 1, furtherincluding: a second control channel controlling supply of fuel to theengine, in place of the first control channel when an abnormalitycondition arises in the first control channel; and the second controlchannel has the transient/steady-state discriminator.
 3. The systemaccording to claim 2, wherein one of the transient/steady-statediscriminators of the first and second control channels has a fourthsensor.
 4. The system according to claim 2, wherein each of the firstand second control channels includes: an acceptability determinerdetermining whether the outputs generated by the sensors of a same typeare within a range that allows the outputs to be considered identical todetermine the sensor output that is usable in the fuel supply control;and a range changer changing the range based on the determined operatingcondition.
 5. A method of controlling a gas-turbine engine having twoturbines including at least a low-pressure turbine and a high-pressureturbine, at least one speed sensor generating an output indicative of arotational speed of the low-pressure turbine, at least one speed sensorgenerating an output indicative of a rotational speed of thehigh-pressure turbine, a temperature sensor generating an outputindicative of a temperature of exhaust gas exiting the low-pressureturbine, and a first control channel inputting the outputs of thesensors and controlling supply of fuel to the engine based on at leastone of the inputted outputs, comprising the steps of: inputting theoutputs generated by the sensors and comparing change rates ordifference of the outputs with corresponding threshold values once everypredetermined time period; and discriminating that the engine is in atransient state when number of the outputs found to be equal to orgreater than the corresponding threshold values are equal to or greaterthan a predetermined value, while discriminating that the engine is in asteady state when number of times that the outputs are found to besmaller than the corresponding threshold values is more than half ofnumber of comparison time.
 6. The method according to claim 5, furtherincluding: a second control channel controlling supply of fuel to theengine, in place of the first control channel when an abnormalitycondition arises in the first control channel; and the second controlchannel has the transient/steady-state discriminator.
 7. The methodaccording to claim 6, wherein one of the transient/steady-statediscriminators of the first and second control channels has a fourthsensor.
 8. The method according to claim 6, further including the stepsof: determining whether the outputs generated by the sensors of a sametype are within a range that allows the outputs to be consideredidentical to determine the sensor output that is usable in the fuelsupply control; and changing the range based on the determined operatingcondition.